Method for identifying next hop

ABSTRACT

Datalink frames or networking packets contain protocol information in the header and optionally in the trailer of a frame or a packet. We are proposing a method in which part of or all of the protocol information corresponding to a frame or a packet is transmitted separately in another datalink frame. The “Separately Transmitted Protocol Information” is referred to as STPI. The STPI contains enough protocol information to identify the next hop node or port. STPI can be used avoid network congestion and improve link efficiency. Preferably, there will be one datalink frame or network packet corresponding to each STPI, containing the data and the rest of the protocol information and this frame/packet is referred to as DFoNP. The creation of STPI and DFoNP is done by the originator of the frame or packet such as an operating system.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No. 11/505,788, filed on Aug. 18, 2006, entitled “Creation and Transmission of Part of Protocol Information Corresponding to Network Packets or Datalink Frames Separately” which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to efficient transfer of datalink frame or network packets in a “custom” network. The network is “custom” as all switches and end nodes need to create or process datalink frames or data packets of special formats.

The OSI, or Open System Interconnection, model defines a networking framework for implementing protocols in seven layers. Most networking protocols do not implement all seven layers, but only a subset of layers. For example, TCP and IP protocol corresponds to layers 4 (TCP) and 3 (IP) respectively. Network packets contain protocol layer information corresponding to the packet. For example, a TCP/IP packet contains a header with both TCP and IP information corresponding to the packet.

The physical layer (layer 1) specifies how bits stream is created on a network medium and physical and electrical characteristics of the medium. The datalink layer (layer 2) specifies framing, addressing and frame level error detection. For outgoing packets to the network, the datalink layer receives network packets from networking layer (layer 3) and creates datalink frames by adding datalink (layer 2) protocol information and passes the frame to the physical layer. For incoming packets from network, datalink layer receives datalink frames from physical layer (layer 1), removes the datalink (layer 2) protocol information and passes network packet to the networking layer. The network layer (layer 3) specifies network address and protocols for end to end delivery of packets.

Network packets contain protocol layer information corresponding to the packet. FIG. 1A illustrates a network packet containing 01001 layer 1, 01002 layer 2, 01003 layer 3, 01004 layer 4 headers, 01005 Data and 01008 layer 1, 01007 layer 2, 01006 layer 3 trailers. FIG. 1B illustrates a network packet with 01011 layer 1, 01012 layer 2 (data link), 01013 layer 3 (networking) and 01014 layer 4 (transport) headers and 01017 layer 1 and 01016 layer 2 trailers and 01015 Data. For each layer, the corresponding header and trailer (if present) together contain all the protocol information required to send the packet/frame to the the consumer of the data in a remote node.

For example, headers/trailers corresponding to a TCP/IP packet in a 10 BaseT Ethernet LAN are:

i) Physical layer header contains Start-of-Stream Delimiter

ii) Data link layer header contains Preamble, Start-of-Frame Delimiter, Ethernet Addresses, Length/Type Field etc.

iii) IP header contains Version, Length, IP Address etc.

iv) TCP header contains Port Numbers, Window, Flags etc.

v) Datalink layer trailer contains 32 bit FCS

vi) Physical layer trailer contains End-of-Stream Delimiter.

When parts of networks get congested and end nodes continue transmitting packets to congested parts of a networks, more and more switches can get congested. This can lead to switches dropping large number of packets, nodes retransmitting the dropped or lost packets and network slowing down.

U.S. Pat. No. 6,917,620 specifies a method and apparatus for a switch that separates the data portion and the header portion. This method has a disadvantage that overhead and logic for separating the data portion and the header portion and then combining the header portion and the data portion before transmission is required. This method also can not consolidate headers from more than one packet for transmission to the next node or delay packet arrival if the destination path of the packet is congested and therefore, can not avoid congestion.

According to claim (1)(c) of U.S. Pat. No. 5,140,582, the header portion of a packet is decoded prior to the receipt of full packet to determine the destination node. This invention can help with faster processing of the packet within a switch. This method can not consolidate headers from more than one packet for transmission to the next node or delay packet arrival if the destination path of the packet is congested and therefore, can not avoid congestion.

U.S. Pat. No. 6,032,190 specifies an apparatus and method of separating the header portion of an incoming packet and keeping the header portion in a set of registers and combining the header portion with the data portion before transmitting the packet. This method has a disadvantage that overhead and logic for separating the data portion and the header portion is required. This method can not consolidate headers from more than one packet for transmission to the next-node or delay packet arrival if the destination path of the packet is congested and therefore, can not avoid congestion.

U.S. Pat. No. 6,408,001 improves transport efficiency by identifying plurality of packets having common destination node, transmitting at least one control message, assigning label to these packets and removing part or all of header. This method has a disadvantage that switches need to identify messages with common destination node and additional logic to remove header and add label. This method can not delay packet arrival if the destination path of the packet is congested and therefore, can not avoid congestion.

BRIEF SUMMARY OF THE INVENTION

It is the object of the present invention to create and transmit part of protocol information separately from the Datalink Frame or Network Packet (DFoNP) containing data. The Separately Transmitted Protocol Information is referred to as STPI. Network congestion can be reduced or avoided using STPI.

According to the invention, there should be at least one DFoNP which contains the data and rest of the protocol information not contained in STPI, corresponding to each STPI. Preferably, there will be only one DFoNP corresponding to each STPI. The STPI and DFoNP together contain all the protocol information required to send the packet/frame to the the consumer of the data in a remote node.

The creation of STPI and DFoNP is done by the originator of the frame or packet such as an operating system in an end node. The format (contents and location of each information in a frame or packet) of the frame or packet containing STPI and DFoNP should be recognized by the final destination of the frame or packet. The format of STPI and DFoNP should also be recognized by switches in the network. So preferably, all STPIs and DFoNP in a given network should be of fixed formats.

Preferably, one or more STPIs are transmitted in a datalink frame or a network packet. The datalink frame containing STPIs is referred to as STPI Frame. The network packet containing STPIs is referred to as STPI packet. The switches in this case should be capable of extracting each STPI in an incoming STPI Frame or STPI packet and forwarding it to the next node in a different STPI Frame or STPI Packet. The switches can add each STPI from an incoming STPI Frame or STPI Packet into an STPI Frame or STPI Packet it creates. Preferably, the layer 2 address in the datalink frame containing multiple STPIs will be the next hop node address.

Optionally, STPI Frame or STPI Packet contains number of STPIs or length of the STPI frame. Optionally, STPI Frame or STPI Packet contains the offset or position of STPIs in the STPI frame—this is required only if STPIs supported by the network are not of fixed length.

Optionally, STPI Frame or STPI Packet does not contain the number of STPIs and switches in the network are capable of identifying the number of STPIs from length of the frame as they are of fixed length.

Preferably, some protocol information contained in STPI may not be contained in the corresponding DFoNP. But protocol information contained in STPI and the corresponding DFoNP need not be mutually exclusive. In this method, the switches obtain both STPI and the corresponding DFoNP before the STPI and the corresponding DFoNP are forwarded. Optionally, STPI need not be forwarded to end node if sufficient protocol information is contained in the corresponding DFoNP.

The proposed invention can be employed for data, control and/or RDMA packets in a network.

The proposed method allows switches to read the more than one STPI, and then delay obtaining the corresponding DFoNP. The DFoNP may be read or forwarded in a different order compared to the order in which STPI are read or forwarded. This method allows switches to optimize resources and packet/frame forwarding efficiency.

STPI contain temporary information such as current node or port number of the node containing the corresponding DFoNP. STPI also contains an address of a buffer containing the corresponding DFoNP or an offset in a buffer where the corresponding DFoNP is stored or an index of the corresponding DFoNP in an array. These information help in associating STPI to the corresponding DFoNP. The exact information contained in STPI whether it is an address or an offset or an index or a combination of these is implementation specific.

Optionally, STPI may contain originating node identifier and a sequence number. Such information can help in reporting errors when STPI or corresponding DFoNP are corrupted or lost.

Optionally, STPI may contain other vendor specific or DFoNP related miscellaneous information.

Optionally, DFoNP may contain some information that help in associating itself with corresponding STPI, such as originating node identifier and a sequence number. Preferably, DFoNP sequence number is same as the sequence number of the corresponding STPI.

Optionally, DFoNP may contain other vendor specific miscellaneous information.

The originating node creating an STPI by creating and initializing one or more data structures. Preferably, there is only one data structure containing STPI.

A switch receiving both frame containing STPI and the DFoNP before forwarding a frame containing STPI or DFoNP to the next switch or node.

Preferably, a switch receiving frame containing STPI before reading the corresponding DFoNP.

A switch can delay transmitting or reading DFoNP after the corresponding STPI is transmitted or received, allowing the switch to optimize its resource usage and improve efficiency.

A switch can read DFoNPs corresponding to a switch port with minimum outbound traffic, ahead of other DFoNPs, thereby improving link efficiency.

The switch modifying temporary information in STPI such as node number or port number corresponding to the node containing corresponding DFoNP and buffer pointer or index or offset for the corresponding DFoNP, when the DFoNP is transmitted to another node.

If the DFoNP and STPI is forwarded to another subnet, layer 2 information in STPI and DFoNP should be updated to be compatible with the subnet to which it is forwarded (for example, in an IP network when a packet moves from Ethernet to ATM, layer 2 protocol information will have to be modified to be made compatible with ATM network).

If STPI contains a multicast or broadcast destination address, the switch transmitting both the DFoNPs and the STPI to all next hop nodes identified by the address.

A switch can delay reading or forwarding the DFoNP after the corresponding STPI is received or forwarded, and vice versa.

A switch may or may not receive or transmit DFoNPs in the same order as the corresponding STPIs are received or transmitted from a switch port.

Optionally, a switch may receive or transmit one or more DFoNP in one frame.

For networks that support layer 5/6/7 (example OSI networks), STPI optionally containing part of or all of layer 5/6/7 information. Preferably, no layer 5/6/7 information may be contained in STPI.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates datalink frames in normal networks.

FIG. 2 illustrates examples of different design options for frames containing STPIs and the corresponding DFoNPs.

FIG. 3 illustrates an option for transmitting STPI and the corresponding DFoNP to next hop node.

FIG. 4 illustrates an option for transmitting STPI and the corresponding DFoNP to next hop node.

FIG. 5 illustrates an option for transmitting STPI and the corresponding DFoNP to next hop node.

FIG. 6 illustrates an option for transmitting STPI and the corresponding DFoNP to next hop node.

FIG. 7 illustrates an option for transmitting DFoNP and optionally, the corresponding STPI to destination node.

FIG. 8 illustrates examples of different design options for frames containing Read-STPI request.

FIG. 9 illustrates examples of different design options for frames containing Read-DFoNP requests.

FIG. 10 illustrates examples of different design options for frames containing Number-of-STPIs message.

FIG. 11 illustrates Ethernet frames adhering to this invention.

FIG. 12 illustrates PCI-Express transactions adhering to this invention

FIG. 13 illustrates examples of design options for frames containing more than one type of requests or messages.

FIG. 14 illustrates how this invention can be used by switches to reorder transmission of DFoNPs.

DETAILED DESCRIPTION OF THE INVENTION

There are a very large number of design options with network component designers with respect to the format of DFoNP, STPI and STPI frame/packet. FIG. 2 illustrates some examples of different formats in which the STPI and the corresponding DFoNP can be created adhering to this invention. The layer 2, layer 3, and layer 4 information that may be present in the DFoNP and STPI may or may not be mutually exclusive and is dependent on specific format or formats of STPI and DFoNP supported by switches and endnodes. Each network will employ only few STPI/DFoNP formats (preferably, as few as 1-3), one each for a subtype of a packet or a frame. Preferably, a network may employ only one format for STPI and one format for DFoNP to reduce complexity in switches and endnodes. STPI should have enough information for the switch to find the port for the next hop.

i) FIG. 2A illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs. All layer 2 02021 02024 (including Destination Node Address used for routing), layer 3 02022 and layer 4 02023 information are in STPI and the DFoNP contains no layer 3 and 4 information. DFoNP contains minimal layer 2 02001 02004 information mandated by datalink layer (an example of optional layer 2 information is the VLAN tag in Ethernet). Frame Type in the frame gives the type of frame, DFoNP 02002, STPI 02012, etc. All data 02003 are in DFoNP. Three STPIs 02013 are sent in a STPI Frame. The destination address 02011 of the STPI Frame is the next hop switch or node address. In this example, 3rd STPI 02014 in the STPI Frame corresponds to the DFoNP shown. The STPI contains the length 02026 of the corresponding DFoNP and the current node number 02025 and current buffer address 02026 containing the corresponding DFoNP. When the DFoNP is transmitted to the next node the node number 02025 and buffer address 02026 in the corresponding STPI are updated.

ii) FIG. 2B illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs. The frames in this network do not have layer 2 trailer. All layer 2 02051 (includes destination node address for routing), RDMA address 02051 for STPI in the destination node, RDMA address 02054 for DFoNP in the destination node, layer 3 02052 and layer 4 02053 information are in STPI. The DFoNP contains no layer 3 and 4 information. In this network, layer 2 02031 02041 contains frame type and hence, no additional field for frame type is present. DFoNP contains layer 2 header 02031 with next hop node address. STPI contains the node number 02055 and an index 02056 to the array containing the corresponding DFoNP. When DFoNP is transmitted to the next node, the node number 02055 and the index 02056 in the corresponding STPI are updated. STPI also contains Source Node Number 02057 (the node number of the node which created the STPI) and STPI sequence number 02058. The STPI 02042 02043 is the only STPI in the STPI Frame.

iii) FIG. 2C illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs. All layer 3 02081 and layer 4 02082 information are in STPI and the DFoNP contains all 02061 layer 2 information. In this network, switches use 02081 layer 3 address to find next hop port. So 02071 layer 2 of STPI Frame does not have next hop node address. Frame Type in the frame gives the type of frame, DFoNP 02062 , STPI 02072, etc. There are 2 STPIs 02073 in the STPI Packet and the first STPI 02074 corresponds to DFoNP. STPI contains the DFoNP Current Node Port Number 02083 corresponding to the node containing DFoNP and an offset 02084 in a buffer to the current location of the corresponding DFoNP. The port number 02083 is the port number on the switch containing STPI. When DFoNP is transmitted to the next node, the port number 02083 and offset 02084 in the corresponding STPI are updated. The port number 02083 is also updated-when STPI is transmitted to the next node. STPI also contains Source Node Number 02085 and a sequence number 02086.

iv) FIG. 2D illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs. STPI contains layer 3 02112, layer 4 02113, and part of layer 2 02111 protocol information (including route to the destination), RDMA address 02111 for STPI in the destination node. DFoNP contains data 02093, part of layer 2 protocol information 02091 02096 and RDMA address 02091 for the DFoNP in the destination node. STPI contains 02115 DFoNP length and the port number 02114 and the buffer address 02115 to the location of the corresponding to DFoNP. When DFoNP is transmitted to the next node, the port number 02114 is reset (as DFoNP is in the same node) and buffer address 02115 in the corresponding STPI are updated. DFoNP Port number 02114 is also updated when STPI is transmitted to the next node. Both STPI and DFoNP contains originating node number 02116 02094 and STPI sequence number 02117 02095. The address in the datalink header 02101 of the STPI Frame is the final destination node address in the subnet indicating all STPIs in the STPI Frame are to the same final destination and switching can be done using STPI Frame address. Frame Type in the frame gives the type of frame, DFoNP 02092, STPI 02102, etc. STPI Frame does not contain the number of STPIs as STPIs are of fixed length and the number of STPIs can be derived from the length of STPI frame. The first STPI 02103 in the frame corresponds to the DFoNP shown.

v) FIG. 2E illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs. STPI contains part of 02143 layer 2 (Layer 2 in STPI contains destination address used for routing), RDMA address 02143 for STPI in the destination node, 02144 part of layer 3 information and all of 02145 layer 4 information. The DFoNP contains 02121 layer 2 protocol information, RDMA address 02121 for DFoNP in the destination node and 02123 part of layer 3 information. Frame Type in the frame gives the type of frame, DFoNP 02122, STPI 02132, etc. STPI corresponding to the DFoNP shown is the first STPI 02133 in the STPI Frame. STPI contains the current node number 02146 and index 02147 to the location of the corresponding to DFoNP. When DFoNP is transmitted to the next node, the node number 02146 and index 02147 in the corresponding STPI are updated. STPI also contains Source Node Number 02141, STPI Sequence Number 02142 and miscellaneous 02148 information. The layer 2 header 02131 of the STPI frame contains next hop node address.

vi) FIG. 2F illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs. The network medium does not support layer 1 header or trailer. STPI contains part of layer 2 02173 (including destination node identifier used for routing) and part of layer 3 02174 protocol information. DFoNP contains layers 2 02151, part of layer 3 02153 and all of layer 4 02154 protocol information. STPI contains the buffer address 02175 and an index 02175 in the buffer to the location of the corresponding to DFoNP. When DFoNP is transmitted to the next node, buffer address 02175 and offset 02175 in the corresponding STPI are updated. STPI also contains Source Node Number 02171, STPI sequence number 02172 and miscellaneous 02176 information. Frame Type in the frame gives the type of frame, DFoNP 02152, STPI 02162, etc. The STPI Frame contains length 02163 of STPIs and since STPIs of this network are of fixed length, the position of the STPIs in the frame can be determined by the switch. Expanded view of the second STPI 02164 in the STPI frame is shown. The layer 2 header 02161 of the STPI frame contains next hop node address.

vii) FIG. 2G illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs. The network medium does not support layer 1 header or trailer. STPI contains part of layer 2 02203(including destination node address for routing), part of layer 3 02204 and part of layer 4 02202 protocol information. DFoNP contains layer 2 02181, part of layer 3 02183 and part of layer 4 02184 protocol information. STPI contains the current node number 02205, an index to a buffer 02206 and an offset 02206 in the buffer to the location of the corresponding DFoNP. When DFoNP is transmitted to the next node, the node number 02205, the index 02206 and the offset 02206 in the corresponding STPI are updated. STPI also contains the Source Node Number 02201 and miscellaneous 02207 information. Frame Type in the frame gives the type of frame, DFoNP 02182, STPI 02192, etc. The STPI Frame contains length 02193 of STPIs and since STPIs of this example are of fixed length, the position of the STPIs in the frame can be determined by the switch. Expanded view of the second STPI 02194 in the frame is shown. The layer 2 header 02191 of the STPI frame contains next hop node address.

viii) FIG. 2H illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs. STPI contains part of layer 2 02233(including destination node address for routing) and all of layer 3 02234 protocol information. The DFoNP contains layer 2 02211 and layer 4 02213 protocol information. STPI contains the length 02235 of the corresponding DFoNP and the current node identifier 02235, buffer address 02236 and an offset 02236 in a buffer to the location of the corresponding DFoNP. When DFoNP is transmitted to the next node, the Current Node identifier 02235, buffer address 02236 and the offset 02236 in the corresponding STPI are updated. STPI also contains Source Node Number 02231 and STPI Sequence Number 02232. Frame Type in the frame gives the type of frame, DFoNP 02212, STPI 02222, etc. The STPI Frame in this example is allowed to have only one STPI 02222. The layer 2 header 02221 of the STPI frame contains next hop node address. Expanded view of the STPI is shown.

ix) FIG. 21 illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs. The network supports protocol layers 5, 6 and 7 in addition to lower layers. STPI contains 02263 layer 2 and 02264 layer 3 information. The DFoNP contains minimal layer 2 02241 protocol information allowed by the datalink layer, layer 4, layer 5, layer 6, and layer 7 02243 protocol information. STPI contains the current node number 02265, a buffer address 02266 in the node and an offset 02266 in the buffer to the location of the corresponding DFoNP. When DFoNP is transmitted to the next node, the node number 02265, the buffer address 02266 and the offset 02266 in the corresponding STPI are updated. STPI also contains Source Node Number 02261 and STPI sequence number 02262. Frame Type in the frame gives the type of frame, DFoNP 02242, STPI 02252, etc. The STPI Frame in this example is allowed to have only one STPI 02253 and 02251 layer 2 of the STPI frame contains address of the destination node in the subnet which is used for routing the STPI frame. Expanded view of the STPI is shown.

x) FIG. 2J illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs. STPI contains layer 2 02293 protocol information (including destination node address for routing). The DFoNP contains 02271 part of layer 2 and all of layer 3 and layer 4 02273 protocol information. Frame Type in the frame gives the type of frame, DFoNP 02272, STPI 02282, etc. The STPI[1] 02284 is the only STPI 02283 in the STPI Frame. STPI contains the current node number 02294 and the buffer address 02295 in the node to the location of the corresponding DFoNP. When DFoNP is transmitted to the next node, the node number 02294 and the buffer address 02295 in the corresponding STPI are updated. STPI also contains Source Node Number 02291 and STPI Sequence Number 02292. DFoNP contains Source Node Number 02274 and a DFoNP sequence number 02275 which is different from STPI sequence number. The layer 2 header 02281 of the STPI frame contains next hop node address. Expanded view of the STPI[1] is shown.

xi) FIG. 2K illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs. STPI contains layer 2 02323 information (including destination node address for routing). The DFoNP contains minimal layer 2 02301 mandated by datalink layer of the subnetwork and all of layer 3 and 4 02302 information. The DFoNP contains control data 02323 such as requests to open a file in addition to data 02323. In this network, layer 2 02301 02311 protocol information contains frame type and hence, no additional field for frame type is present. The STPI[1] 02313 is the only STPI 02312 in the STPI Frame. STPI contains the length 02324 of the corresponding DFoNP and the node number 02324 and the buffer address 02325 in the node to the location of the corresponding to DFoNP. When DFoNP is transmitted to the next node, the node number 02324 and buffer address 02325 in STPI are updated. STPI also contains the Source Node Number 02321 and STPI sequence number 02322. DFoNP contains Source Node Number 02304 and a DFoNP Sequence Number 02305 which is different from STPI sequence number. Expanded view of STPI[1] is shown.

xii) FIG. 2L illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs. STPI contains layer 2 02354 (including destination node address for routing) and layer 3 information 02353 and part of layer 5/6/7 02357 protocol information. The DFoNP contains minimal layer 2 Header 02331 mandated by datalink layer of the subnet, layer 4 02333 and part of layer 5/6/7 02334 protocol information. The DFoNP contains control data 02335 such as requests to open a file in addition to data 02335. Frame Type in the frame gives the type of frame, DFoNP 02332, STPI 02342, etc. The STPI[1] 02344 is the only STPI 02343 in the STPI Frame. STPI contains the node number 02355 and buffer address 02356 in the node to the location of the corresponding DFoNP. When DFoNP is transmitted to the next node, the node number 02355 and buffer address 02356 in the corresponding STPI are updated. STPI also contains the Source Node Number 02351 and STPI sequence number 02352. The layer 2 header 02341 of the STPI frame contains next hop node address. Expanded view of the STPI[l] 02344 is shown.

xiii) FIG. 2M illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs. STPI contains layer 2 02386 (including destination node identifier used for routing), layer 3 02385 and layers 5/6/7 02387 protocol information. The DFoNP contains layers 2 02361, layer 3 02363 and layer 4 02364 protocol information. Frame Type in the frame gives the type of frame, DFoNP 02362, STPI 02372, etc. STPI frame contains two STPIs 02373 and expanded view of the 2nd STPI (STPI[2]) 02376 is shown. The STPI frame contains offsets 02374 to all STPIs in the frame. The network in this example supports more than one length for STPIs. STPI[1] offset 02374 gives the location of the first STPI (STPI[l] 02375) in the STPI frame. STPI[2] offset 02374 gives the location of the second STPI in the STPI frame. Offsets in this example are with respect to beginning of the frame. STPI contains the node number 02381 and buffer address 02382 in the node to the location of the corresponding DFoNP. When DFoNP is transmitted to the next node, the node number 02381 and buffer address 02382 in STPI are updated. STPI also contains Source Node Number 02383 and STPI sequence number 02384. The layer 2 header 02371 of the STPI frame contains next hop node address.

xiv) FIG. 2N illustrates example formats for DFoNP, the corresponding STPI and an STPI frame which contain STPIs. STPI contains layer 2 02415 (including destination node identifier used for routing) protocol information. The DFoNP contains layer 2 02391, layers 3 02394 and layer 4 02394 protocol information. Frame Type in the frame gives the type of frame, Read Completion 02392 for DFoNP frame and Write 02402 for STPI frame. The STPI Frame contains the length of write 02403 (which is the length of STPI[1] 02403 and STPI[2] 02404) and address 02403 for the write. DFoNP contains Read Requester ID 02393 (Identifier) and a tag 02393 to identify the read request. DFoNP also contains address 02393 from which the layer 3/4 headers and the data 02395 is read and the length 02393 of the the read. The STPI Frame contains two STPIs and expanded view of the 2nd STPI (STPI[2]) 02404 is shown. STPI contains the node number 02411 and buffer address 02412 in the node to the location of the corresponding DFoNP and the length of the DFoNP 02416. These information are used to read the corresponding DFoNP. When DFoNP is transmitted to the next node, the node number 02411 and buffer address 02412 in STPI are updated. STPI also contains Source Node Number 02413, STPI Sequence Number 02414 and Miscellaneous 02416 information. The layer 2 header 02401 of the STPI frame contains next hop node address.

Below five options for transferring STPI and the corresponding DFoNP from one node to another, are described. One of the first 4 methods can be used for transferring STPI and the corresponding DFoNP from the originating node or a switch to another switch or end node. The fifth method can be used for transferring STPI and the corresponding DFoNP to a destination end node:

i) FIG. 3 illustrates one of the options that could be used in a given network for transmitting STPI and DFoNP to the next hop node. In this option a switch/node responds to Read-STPI request by transmitting STPIs. The switch/node receiving STPIs sends Read-DFoNP requests using the information contained in STPIs to fetch the corresponding DFoNPs. A frame containing a Read-STPI request is called Read-STPI Frame. A frame containing Read-DFoNP requests is called Read-DFoNP Frame. In FIG. 5A, Switch/Node A 03001 contains an STPI 03003 and the corresponding DFoNP 03004 to be transmitted to the Switch/Node B 03002. In FIG. 3A, the Switch/Node B transmits Read-STPI Frame 03005 to the Switch/Node A giving the maximum number of STPIs that can be transmitted. The maximum number of STPIs 03005 are 5 in the example. In FIG. 3B, the Switch/Node A responds by sending an STPI frame 03011 containing the STPI 03003 (the STPI frame in this example can contain upto 5 STPIs). In FIG. 3C, the Switch/Node B decides to fetch the DFoNP corresponding to the STPI 03003 and sends Read-DFoNP Frame 03021 to the Switch/Node A containing the Read-DFoNP request for the DFoNP 03004. The Read-DFoNP request contains the location (a location could be a buffer address or an offset in a buffer or an index or a combination of addresses, offsets or indexes) of the DFoNP 03004 in the Switch/Node A. The location of the DFoNP to be used in Read-DFoNP request will be present or can be derived from the contents of the corresponding STPI 03003. In FIG. 3D, the Switch/Node A responds to the Read-DFoNP request for the DFoNP by sending the DFoNP 03004. In FIG. 3E, the STPI 03003 is updated with the identifier of the Switch/Node B and the location of the DFoNP 03004 in the Switch/Node B.

ii) FIG. 4 illustrates another option for transmitting STPI and the corresponding DFoNP to the next hop node. In this option, a switch/node transmits STPIs followed by DFoNPs corresponding to the STPIs transmitted. In FIG. 5A Switch/Node A 04001 contains an STPI 04003 and the corresponding DFoNP 04004 to be transmitted to the Destination Node B 04002. In FIG. 4B, the Switch/Node A transmits an STPI Frame 04011 containing the STPI 04003 to the Switch/Node B. In FIG. 4C, the Switch/Node A transmits the DFoNP 04004 to the Switch/Node B. In FIG. 4D, the Switch/Node B updates the STPI 04003 with the location of the DFoNP 04004 in the Switch/Node B.

iii) FIG. 5 illustrates another option for transmitting STPI and the corresponding DFoNP to the next hop node. In this option a switch/node transmits STPIs and the switch/node receiving STPIs sends Read-DFoNP requests using information contained in STPIs to fetch the corresponding DFoNPs. In FIG. 5A Switch/Node A 05001 contains an STPI 05003 and the corresponding DFoNP 05004 to be transmitted to the Switch/Node B 05002. In FIG. 5B Switch/Node A transmits a frame 05011 containing the STPI to the Switch/Node B. In FIG. 5C, the Switch/Node B decides to fetch the DFoNP corresponding to the STPI and sends Read-DFoNP Frame 05021 to the Switch/Node A containing DFoNP request for the DFoNP 05004. The DFoNP request contains the location of the DFoNP 05004. The location of the DFoNP used in the Read-DFoNP request will be present or can be derived from the contents of the corresponding STPI 05003. In FIG. 5D, the Switch/Node A responds to the Read-DFoNP request by transmitting the DFoNP 05004. In FIG. 5E, the STPI 05003 is updated with identifier of Switch/Node B and the location of the corresponding DFoNP 05004 in the Switch/Node B.

iv) FIG. 6 illustrates another option for transmitting STPI and DFoNP to the next hop node. In this option a switch/node responds to Read-STPI request by transmitting STPIs followed by the corresponding DFoNPs. In FIG. 6A Switch/Node A 06001 contains an STPI 06003 and the corresponding DFoNP 06004 to be transmitted to the Switch/Node B 06002. The Switch/Node B transmits Read-STPI Frame 06005 to the Switch/Node A giving the maximum number of STPIs that can be transmitted. The maximum number of STPIs 06005 is 0 in the example indicating that all STPIs can be transmitted. In FIG. 6B, the Switch/Node A responds by sending an STPI frame 06011 containing all STPIs to be transmitted to the Switch/Node B. In FIG. 6C, the Switch/Node A transmits the DFoNP 06004 corresponding to the STPI to the Switch/Node B. In FIG. 6D, the STPI 06003 is updated with identifier of the Switch/Node B and the location of the corresponding DFoNP 06004 in the Switch/Node B.

v) FIG. 7 illustrates an option which can be used for transmitting DFoNP and optionally the corresponding STPI from a switch/node to a destination node: In this option DFoNP is transmitted to the destination node and then optionally, the corresponding STPI is transmitted. In FIG. 7A, Switch/Node A 07001 contains an STPI 07003 and the corresponding DFoNP 07004 to be transmitted to the Destination End Node B 07002. In FIG. 7B, Switch/Node A transmits the DFoNP 07004 to the Destination End Node B and updates the STPI 07003 with the location (DMA address) of the DFoNP in the Destination End Node B. In FIG. 7C, Switch/Node A transmits the STPI in an STPI frame 07021 to the Destination End Node B. In FIG. 7D, both STPI 07003 and DFoNP 07004 are received by End Node B.

A switch can employ one of the STPI and DFoNP transfer options (strategies) listed above, for each port. Both ports on a point-to-point link must agree to the same frame transmitting option. All ports on a link or bus must follow the same frame transmitting option. Preferably, a network employs only one of the four STPI/DFoNP transfer options listed in FIG. 3, FIG. 4, FIG. 5 and FIG. 6. Preferably, a network also employs the STPI/DFoNP transfer option listed in FIG. 7. For the option corresponding to FIG. 7, updating STPI with address (location) of DFoNP in the end node is optional.

If DFoNPs do not contain information (such as originating node identifier, DFoNP identifier, DFoNP address in previous node, etc.) that allow a DFoNP to be mapped to the corresponding STPI, then the DFoNPs must be transmitted in the same order as requested in Read-DFoNP frame/s with design options listed in FIG. 3 and FIG. 5. With design options listed in FIG. 4 and FIG. 6, if DFoNPs do not contain information that allow the DFoNP to be mapped to the corresponding STPI, DFoNPs must be transmitted in the same order as the corresponding STPIs are transmitted. This will allow switches to identify STPI corresponding to an DFoNP that is received.

There are a very large number of design options with network component designers with respect to the format of Read-STPI request and Read-STPI Frames containing Read-STPI request. FIG. 8 illustrates some examples of different formats in which the Read-STPI Frames can be created adhering to this invention. Preferably a given network employs only one format (design option) for Read-STPI request to keep the design of switches and end nodes simple.

i) FIG. 8A illustrates a Read-STPI frame with Frame Type

“Read-STPI” 08001 and “Number of STPIs” 08002 set to 3. The frame also contains Miscellaneous 08003 field.

ii) FIG. 8B illustrates a Read-STPI frame in a network where explicit frame type specification is not required. The frame specifies an address 08011 for read (the location of the STPIs) in the node receiving the Read-STPI Frame. The frame also provides the length 08012 for read. The address where STPIs are stored can be dynamically configured on the switch for each node/switch it is connected to.

iii) FIG. 8C illustrates a Read-STPI frame in a network without layer 1 headers or trailers. Frame Type 08021 is “Read-STPI”. The “Number of STPIs” 08022 is 0 indicating permission to transmit an STPI Frame with as many STPIs for the node transmitting Read-STPI Frame as possible, from the node receiving the Read-STPI Frame. The frame also contains a Miscellaneous 08023 field.

iv) FIG. 8D illustrates a Read-STPI frame in a network without layer 1 headers or trailers. Layer 2 header 08031 contains Frame Type (Read-STPI). The “Number of STPIs” 08032 is −1 indicating permission to transmit all STPIs for the node transmitting Read-STPI Frame, from the node receiving the Read-STPI Frame.

A Read-DFoNP Frame contains one or more Read-DFoNP requests and each Read-DFoNP request contains the location of the requested DFoNP. There are a very large number of design options with network component designers with respect to the format of Read-DFoNP requests and Read-DFoNP Frames containing Read-DFoNP requests. FIG. 9 illustrates some examples of different formats in which the Read-DFoNP Frame can be created adhering to this invention. Preferably, a given network employs only one format (design option) for Read-DFoNP request to keep the design of switches and end nodes simple.

i) FIG. 9A, illustrates a Read-DFoNP frame with Frame Type 09001 “Read-DFoNP” and “Number of Read-DFoNP requests” 09002 set to 2. The DFoNP[1] 09003 and DFoNP[2] 09004 buffer addresses provide the location of the DFoNPs in the node receiving the Read-DFoNP Frame. The frame also contains Miscellaneous 09005 field.

ii) FIG. 9B illustrates a Read-DFoNP frame in a network where explicit frame type specification is not required. Frame specifies an address 09011 for read (the location of the DFoNP) in the node receiving the Read-DFoNP Frame. The frame also provides the length 09012 for read.

iii) FIG. 9C illustrates Read-DFoNP frame in a network without layer 1 headers or trailers. Frame Type 09021 is “Read-DFoNP”, the “Number of Read-DFoNP requests” 09022 is 3. Each Read-DFoNP request contains a buffer address and an offset. The DFoNP[1] 09023, DFoNP[2] 09024 and DFoNP[3] 09025 buffer addresses and offsets provide the location of the DFoNPs in the node receiving the Read-DFoNP Frame.

iv) FIG. 9D illustrates a Read-DFoNP feame in a network without layer 1 headers or trailers. Frame Type (Read-DFoNP) is contained in layer 2 header 09031. Only one Read-DFoNP request 09032 is allowed in the frame and the the Read-DFoNP request gives the index of the DFoNP to be read.

Optionally, a switch or node can send the number of STPIs available for transmission to the next hop node or switch. There are a very large number of design options with network component designers with respect to the format of Number-of-STPIs message and Number-of-STPIs Frames containing Number-of-STPIs message. FIG. 10 illustrates some examples of different formats in which the Number-of-STPIs Frame can be created adhering to this invention. Preferably a given network employs only one format for Number-of-STPI message to keep the design of switches and end nodes simple.

i) FIG. 10A, illustrates a Number-of-STPIs frame with Frame Type 10001 “Number-of-STPIs” and “Number of STPIs” 10002 set to 3. The frame also contains a Miscellaneous 10003 field.

ii) FIG. 10B illustrates Number-of-STPIs frame in a network where explicit frame type specification is not required. Frame specifies an address 10011 to the location where value of Number of STPIs will be written and the length 10012 of the field to be written. The next field contains data (Number of STPIs) 10013 for the write, which is 2.

iii) FIG. 10C illustrates Number-of-STPIs frame in a network without layer 1 headers or trailers. Frame Type 10021 is “Number-of-STPIs”. The “Number of STPIs” 10022 is 3. The frame also contains a Miscellaneous 10023 field.

iv) FIG. 10D illustrates a Number-of-STPIs frame in a network without layer 1 headers or trailers. Layer 2 header 10031 contains Frame Type (Number-of-STPIs). The “Number of STPIs” 10032 is 1.

The network described in this invention can be connected to an I/O card (in a server or embedded system) or to a PCI bus.

i) The switch corresponding to this invention can be connected to an Ethernet card.

-   -   a) A recommended frame format for use with Ethernet is as         follows:         -   1) Ethernet header contains destination MAC: The network can             use next hop MAC address in the             STPI/DFoNP/Read-STPI/Read-DFoNP/Number-of-STPIs frame.         -   2) Ethernet header contains source MAC address: A DFoNP             frame can contain the MAC address of the originating node in             this field. All other types of frames (STPI, Read-STPI,             Read-DFoNP, Number-of-STPI) can contain MAC address of the             node transmitting the frame in this field.         -   3) The Ethernet header contains length field as per Ethernet             Protocol standard.         -   4) The first byte of the data field contains the             “Frame-Type”: one bit each for STPI, DFoNP, Read-STPI,             Read-DFoNP and Number-of-STPIs.         -   5) Each STPI will contain the final destination MAC address.             Optionally, each STPI can also contain source MAC address of             the the originating node of the STPI.         -   6) The formats specified examples such as FIG. 2A, FIG. 2C             etc., can be used with Ethernet.         -   7) The Ethernet trailer contains FCS for the frame.     -   b) FIG. 11A illustrates an example of DFoNP and STPI frames         which can be used with Ethernet. FIG. 11B illustrates Read-DFoNP         frame which can be used with Ethernet.         -   1) Destination MAC address 11001 in DFoNP frame is the MAC             address corresponding to the port or node (next hop node)             receiving the frame. If switches are designed to ignore             Destination MAC address in a DFoNP frame, the final             destination node MAC address could be used in the             Destination MAC address field.         -   2) Source MAC address 11002 in the DFoNP frame is the MAC             address of the node that created the DFoNP.         -   3) The length field 11003 provides the length as per             Ethernet Protocol standard.         -   4) The first field in the data portion of Ethernet Frame is             Frame Type 11004 and Frame Type of DFoNP frame is DFoNP             (DFoNP bit is set).         -   5) The DFoNP contains layer 3 11005, layer 4 11006 protocol             information and data 11007.         -   6) Destination MAC address 11011 in the STPI frame is the             MAC address corresponding to the port or node (next hop             node) receiving the frame.         -   7) Source MAC address 11012 in the STPI frame is the MAC             address corresponding to the port transmitting the frame.         -   8) The length field 11013 provides the length as per             Ethernet Protocol standard.         -   p9) The first field in the data portion of the Ethernet             Frame is Frame Type 11014 and Frame Type of STPI frame is             STPI (STPI bit is set).         -   10) The STPI frame in this example contains 2 STPIs 11015.         -   11) Expanded view of the second STPI 11016 is shown.         -   12) Each STPI contains the Final Destination MAC address             11021 for the STPI and the corresponding DFoNP. Switches can             use this address for routing.         -   13) The STPI contains the Source MAC Address 11022 of the             Ethernet port through which the STPI entered the Ethernet             LAN.         -   14) STPI contains “Destination STPI Address” 11023 which is             the address to be used for RDMA Writing the STPI in the             destination node.         -   15) STPI contains “Destination DFoNP Address” 11024 which is             the address to be used for RDMA Writing the corresponding             DFoNP in the destination node.         -   16) The STPI contains the MAC address of the node containing             DFoNP 11025, buffer address 11026 of the DFoNP in this node             and length 11026 of the DFoNP. These fields are used to             create Read-DFoNP request.         -   17) After an STPI an STPI frame is received, the next hop             node can initiate read for the corresponding DFoNP. FIG. 11B             illustrates a Read-DFoNP frame containing 3 Read-DFoNP             requests.         -   18) The destination MAC address 11031 in the Read-DFoNP             frame is the “DFoNP Current Node MAC address” 11025 from the             STPI.         -   19) The source MAC address in the Read-DFoNP frame is the             MAC address corresponding to the port transmitting the             Read-DFoNP Frame.         -   20) The length field 11013 provides the length as per             Ethernet Protocol standard.         -   21) The first field in the data portion of the Ethernet             Frame is Frame Type 11034 and Frame Type of Read-DFoNP frame             is “Read-DFoNP” (“Read-DFoNP” bit is set).         -   22) The Number of DFoNPs 11035 being requested from the node             receiving Read-DFoNP frame is 3 in this example.         -   23) The DFoNP buffer address 11036 and the length 11036 of             DFoNP in Read-STPI frame are from DFoNP Current Buffer             Address 11026 and DFoNP Length 11026 fields in STPI.     -   ii) If the switch corresponding to this invention is connected         to a PCI bus, it behaves like an end node. The switch will use         PCI transactions to communicate with the server.     -   a) The host (in turn the PCI root bridge) can use PCI memory         write transaction to transfer STPIs to a switch corresponding to         this invention OR the switch can use PCI memory read transaction         to read STPIs. The host can use PCI memory write transaction to         write the address of the memory location holding STPIs which the         switch can use for PCI Memory Read transaction.     -   b) The switch can use PCI read transaction to read each DFoNP         using the buffer address contained in the corresponding STPI.     -   c) The host (in turn the PCI root bridge) can optionally use PCI         write transaction to write the number of STPIs to a switch         corresponding to this invention.     -   d) The switch can use PCI memory write to write DFoNPs and STPIs         to the memory of the destination node.     -   e) FIG. 12 illustrates an example of transaction formats which         can be used within PCI Express™ (PCI Express™ is a trade mark of         PCI-SIG) transactions for transferring STPIs and DFoNPs from         root bridge to a switch corresponding to this invention and vice         versa.         -   1) Example in FIG. 12A illustrates format of PCI Express             Read Completion containing DFoNP, from a root bridge in             response to a Memory Read request from a switch. The first             field of PCI Express Read Completion data provides the Frame             Type 12001 which is DFoNP. The rest of the Read Completion             data is layer 3/4 protocol information 12002 and Data 12003             being transmitted to the remote node.         -   2) Example in FIG. 12B illustrates format of PCI Express             Read Completion containing STPIs, from a root bridge in             response to a Memory Read request from a switch. The first             field of data provides the Frame Type 12011 which is STPI.             The second field in data is “Number of STPIs” 12012 which is             3 followed by three STPIs 12013. Each STPI contains “Final             Destination Node Identifier” 12021 which is used by switches             for routing, Source Node Identifier 12022 which is the             identifier of the node that created the STPI, “Destination             STPI Address” 12023 to be used for RDMA Writing STPI in the             destination, “Destination DFoNP Address” 12024 to be used             for RDMA Writing the corresponding DFoNP in the destination,             “DFoNP Current Node ID” 12025, DFoNP Length and DFoNP             Current Address 12026 to be used for reading DFoNP from the             node where it is currently stored. The DFoNP Length field             12026 is also used for RDMAing DFoNP to the memory of the             destination node.         -   3) Example in FIG. 12C illustrates a PCI Express Memory             Write transaction containing DFoNP, from a switch to a root             bridge . The first field of PCI Express Memory Write             transaction data provides the Frame Type 12031 which is             DFoNP. The rest of the Read Completion data is layer 3/4             information 12032 and Data 12033 that arrived from the             remote node.         -   4) Example in FIG. 12D illustrates a PCI Express Memory             Write transaction containing STPIs, from a switch to a root             bridge. The first field of PCI Express Memory Write data             provides the Frame Type 12041 which is STPI. The second             field in the data is “Number of STPIs” 12042 which is 2             followed by two STPIs 12043. Each STPI contains “Final             Destination Node Identifier” 12051 which is used by switch             for routing, Source Node Identifier 12052 which is the             identifier of the node that created the STPI, a             miscellaneous field 12053, “DFoNP Current Node Identifier”             12054, DFoNP Current Buffer Address 12055 and DFoNP Length             12055 to be used for reading DFoNP from the node where it is             currently stored. The DFoNP Length field 12055 is also used             for doing PCI Express Memory Write transaction to the root             bridge (DMAing DFoNP to the memory of the destination node).             The DFoNP and STPI are DMAed into read buffers provided by             the destination node.

When destination address contained in an STPI is a Multi-cast and Broadcast address, both STPI and DFoNP are transmitted to all next hop nodes identified by the Multi-cast or Broadcast address.

When STPI or DFoNP frames are corrupted or lost, switches and nodes may employ retransmission of the corrupted or lost frame. The retransmission policy and error recovery are link (example PCI) and vendor specific.

Some networks allow more than one type of content to be present in the same frame. The types of contents are STPI, DFoNP, Read-STPI request, Read-DFoNP request and Number-of-STPIs message.

-   -   i) FIG. 13A illustrates a frame containing both Number-of-STPIs         message and Read-DFoNP requests. The Frame Type 13001 is a         bit-OR of “Number-of-STPIs” and “Read-DFoNP”. The “Number of         STPIs” 13002 is 5 indicating that there are 5 STPIs available to         be transmitted to the receiving node. The “Number of DFoNPs”         13003 is 3 and the receiving node is expected to respond to the         request by transmitting the three DFoNPs requested.     -   ii) FIG. 13B illustrates a frame containing both Read-STPI         request and Read-DFoNP requests. The Frame Type 13011 is a         bit-OR of “Read-STPI” and “Read-DFoNP”. The “Number of STPIs”         field 13012 is 2 and the “Number of DFoNPs” field 13013 is 3.         The node receiving the frame is expected to respond with two         STPIs and the three requested DFoNPs.

FIG. 14 illustrates an example of reading DFoNPs in a different order compared to the order in which STPIs are received. In FIG. 3A, Switch A 14001 has 3 DFoNPs 14004 to be transmitted to Switch B 14002. The Switch A forwards 3 STPIs corresponding to the DFoNPs in an STPI frame 14003 to Switch B. The Switch B has 10 STPIs in its queue 14006 for its link to node D. The switch B has no STPIs in its queue 14005 for its link to node C. In FIG. 14B, the switch identifies that STPI[1] and STPI[2] received are for node D and adds STPI[1] and STPI[2] to the queue 14006 for the node D. The Switch B delays reading DFoNP[1] and DFoNP[2] since there are a large of STPIs already queued for the node D. The Switch B identifies that STPI[3] received is for the node C and queues STPI[3] to the queue 14005 for the node C. The Switch B sends Read-DFoNP Frame 14013 to the Switch A with DFoNP[3] address.

If STPI contains a priority or QoS field, a switch can use it for controlling the order in which DFoNPs are read. Similarly, a priority or QoS field in STPI or DFoNP could be used by switches or nodes to control the order in which STPIs are transmitted to the next node.

A network corresponding to this invention could be used to connect a server or servers to storage devices (such as disks, disk arrays, JBODs, Storage Tapes, DVD drives etc.). iSCSI and iSER (iSCSI Extensions for RDMA) are examples in which SCSI commands and SCSI data are transmitted using networks technologies used for server interconnect.

ADVANTAGES

A switch can delay receiving DFoNP for paths which are already congested.

A switch can read DFoNP corresponding to a lightly loaded link ahead of other DFoNPs and transmit STPI and DFoNP more quickly to the lightly loaded link improving link efficiency.

A switch can delay reading DFoNPs based on QoS or priority field in STPI.

A switch can optimize switch resources, memory and frame/packet queues as congestions are minimized by delaying DFoNPs for ports which are already congested.

The switch can ensure higher throughput on all links by rearranging order in which DFoNPs are read. 

1. A method implemented in a first network switch for switching Data Link frames, wherein said first network switch is used for interconnecting network nodes in a network, said method comprising: (a) receiving information required to identify at least one next hop node of a first Data Link frame in a second Data Link frame, wherein said second Data Link frame is received from a second network node, wherein said information and said first Data Link frame are transmitted separately by said second network node, wherein a next hop node of said first Data Link frame is a third network node to which said first Data Link frame is to be transmitted by said first network switch; (b) identifying said third network node before receiving said first Data Link frame by using said information required to identify at least one next hop node of said first Data Link frame, wherein said first Data Link frame is not used for identifying said third network node; (c) receiving said first Data Link frame from said second network node after identifying said third network node to which said first Data Link frame is to be transmitted; and (d) transmitting said first Data Link frame to said third network node.
 2. The method of claim 1 further comprising: transmitting said first Data Link frame to only said one next hop node, wherein said information identifies only one next hop node.
 3. The method of claim 2 further comprising: transmitting information required to identify at least one next hop node of said first Data Link frame to said third network node in a third Data Link frame.
 4. The method of claim 2 further comprising: transmitting a first request to said second network node to transmit said first Data Link frame to said first network switch.
 5. The method of claim 4 further comprising: receiving Data Link frames in a first set of Data Link frames in a first order different from a second order in which information required to identify next hop nodes for the Data Link frames in said first set of Data Link frames, is received.
 6. The method of claim 5 further comprising: receiving Data Link frames in said first set of Data Link frames in said first order different from said second order in which information required to identify next hop nodes for the Data Link frames in said first set of Data Link frames, is received, wherein said first order is dependent on the network load on the switch ports on which the Data Link frames in said first set of Data Link frames, are to be transmitted out of said first network switch.
 7. The method of claim 3 further comprising: transmitting Data Link frames in a second set of Data Link frames in a third order different from a fourth order in which the corresponding information required to identify next hop nodes for the Data Link frames in said second set of Data Link frames, is transmitted out of said first network switch.
 8. The method of claim 7 further comprising: transmitting Data Link frames in said second set of Data Link frames in said third order different from said fourth order in which the corresponding information required to identify next hop nodes for the Data Link frames in said second set of Data Link frames, is transmitted out of said first network switch, wherein said third order is dependent on network load on a first set of network switches which receive the Data Link frames in said second set of Data Link frames, from said first network switch.
 9. The method of claim 1 further comprising: receiving priority of said first Data Link frame in said second Data Link frame.
 10. A method implemented in a first network switch for switching network packets, wherein said first network switch is used for interconnecting network nodes in a network, said method comprising: (a) receiving information required to identify at least one next hop node of a first network packet, wherein said information is received by said first network switch from a second network node in a first Data Link frame, wherein said information and said first network packet are transmitted separately by said second network node, wherein said first Data Link frame does not contain said first network packet, wherein a next hop node of said network packet is a third network node to which said first network packet is to be transmitted by said first network switch; (b) identifying said third network node before said first network packet is received by using said information required to identify at least one next hop node of a first network packet, wherein said first network packet is not used for identifying said third network node; (c) receiving said first network packet from said second network node after identifying said third network node to which said first network packet is to be transmitted; and (d) transmitting said first network packet to said third network node.
 11. The method of claim 10 further comprising: transmitting said first network packet to only said one next hop node, wherein said information identifies said only one next hop node.
 12. The method of claim 11 further comprising: receiving said first network packet from said second network node in a second Data Link frame.
 13. The method of claim 11 further comprising: transmitting information required to identify at least one next hop node of said first network packet to said third network node.
 14. The method of claim 11 further comprising: transmitting a first request to said second network node to transmit said first network packet to said first network switch.
 15. The method of claim 14 further comprising: receiving network packets in a first set of network packets in a first order different from a second order in which the corresponding information required to identify next hop nodes for the network packets in said first set of network packets, is received.
 16. The method of claim 13 further comprising: transmitting network packets in a second set of network packets in a third order different from a fourth order in which corresponding information required to identify next hop nodes for the network packets in said second set of network packets, is transmitted out of said first network switch.
 17. The method of claim 10 further comprising: receiving priority of said first network packet in said first Data Link frame.
 18. A first network switch implemented in hardware used for switching Data Link frames and used for interconnecting network nodes in a network, said network switch comprising: (a) a mechanism to receive information required to identify at least one next hop node of a first Data Link frame, wherein said information is received from a second network node in a first PCI Express memory transaction, wherein said information and said first Data Link frame are transmitted separately by said second network node, wherein said first PCI Express memory transaction does not contain said first Data Link frame, wherein a next hop node of said first Data Link frame is a third network node to which said first Data Link frame is to be transmitted by said first network switch; (b) a mechanism to receive said first Data Link frame from said second network node; (c) a mechanism to identify said third network node by using said information required to identify at least one next hop node of said first Data Link frame; and (d) a transmission mechanism to transmit said first Data Link frame to said third network node.
 19. The first network switch of claim 18 comprising: said mechanism to receive said first Data Link frame from said second network node, wherein said first Data Link frame is received in a second PCI Express memory transaction.
 20. The first network switch of claim 19 comprising: said transmission mechanism to transmit said first Data Link frame to only one said next hop node, wherein said information identifies only one next hop node. 